1. Field of the Invention
The present invention relates generally to computer systems, and more particularly but not exclusively to search engines.
2. Description of the Background Art
The Internet is an example of a computer network. On the Internet, consumers on client computers may access various types of information resident in server computers. A server computer that provides information over the Internet is also referred to as a “web server” or a “website”. A website may provide information about various topics, or offer goods and services. A website may comprise a plurality of downloadable documents, such as web pages and files. A consumer may use a web browser to receive and view a web page.
Because of the large number of websites on the Internet, searching the Internet for specific information usually requires the services of a search engine. Generally speaking, a search engine helps consumers look for relevant web pages. A typical search engine accepts a word or a phrase, referred to herein as a “keyword.” The search engine employs the keyword in conjunction with its search algorithm to find matching web pages. The links to matching web pages are presented to the consumer in the form of a listing referred to as “search results.” Typical search results list the matching web pages as clickable links, with each link pointing to a corresponding web page. Examples of websites with search engines include Yahoo, Google, and Alta Vista.
A search engine includes an index (also referred to as a “catalog”) containing links to web pages responsive to particular keywords. Entries to the index may be obtained by accepting submissions from website operators, as in the case of so-called “human-powered search engines,” by using a crawler, or both. Crawler-based search engines employ a crawler (also referred to as a “spider” or “robot”) to automatically fetch web pages over the Internet. A crawler may be given an address of a web page, fetch that web page, then fetch web pages pointed to by that web page, and so on. Web pages fetched by the crawler are stored in the index.
A keyword and a link responsive to the keyword are also collectively referred to as a “keyword-link combination.” A typical search engine ranks keyword-link combinations stored in an index based on the relevance of the link to the keyword. A keyword-link combination may be ranked based on the number of times the keyword appears on the web page pointed to by the link. The web page pointed to by the link may be further ranked based on the number and credibility of other web pages pointing to it. For example, when a keyword appears the same number of times on two different web pages, the web page referenced by more, credible web pages gets the higher ranking. When a consumer employs a search engine to search the Internet using a keyword, the search engine sifts through the index to find the highest ranked keyword-link combinations having that keyword. Links of the highest ranked keyword-link combinations are presented to the consumer as search results.